This invention relates to test and measurement instruments and, more particularly, to test and measurement instruments using non-periodic functions for bandwidth multiplication.
Digital oscilloscopes have limited input bandwidths. The bandwidth of an input signal is limited to the input bandwidth of the oscilloscope. In U.S. Patent Application Publication 2004/0128076 to Pupalaikis, et al., a real-time oscilloscope is disclosed with an increased usable bandwidth. The real-time oscilloscope splits the input signal into multiple split signals. One split signal is digitized. Simultaneously, the other split signals are frequency shifted to a baseband frequency range and digitized. The digitized frequency-shifted signals are frequency shifted to their original frequency range and then combined with the other digitized signals to create a representation of the input signal. By frequency shifting sub-bands of the input signal to be within the bandwidth of their respective digitizers, an input signal having a frequency range larger than the input bandwidth of a digitizer may be acquired using the lower bandwidth digitizers.
However, periodic signals are used in frequency shifting the sub-bands to be within the bandwidth of a digitizer. As a result, detrimental effects from coherent spurious components are more pronounced.
Accordingly, a need remains for an improved method and apparatus for reconstructing signals from sub-band signals.